1. Field of the Invention
Aspects of the invention relate to a multi-user Multiple-Input Multiple-Output (MIMO) communication, and more particularly, to a MIMO communication system and method that can control a transmitting antenna based on a power of a transmission signal.
2. Description of the Related Art
Currently, research to provide a voice service and various types of multimedia services and to support high-quality and high-speed data transmission is quite active. For example, research on a Multiple-Input Multiple-Output (MIMO) scheme using a plurality of channels in a spatial area is a rapidly advancing technology. The MIMO scheme increases a number of channel bits within a limited frequency resource using multiple antennas and thereby provides a high data transmission rate. The MIMO scheme uses multiple transmitting/receiving antennas in a wireless channel environment and thus theoretically provides channel capacity that is in proportion to the smaller of the number of transmitting antennas and the number of receiving antennas. Research to increase the overall channel capacity of a multi-user MIMO system in a multi-user environment where one base station supports a plurality of terminals is also quite active.
In an uplink of the multi-user MIMO system, a multi-user transmits data to a base station. In a downlink of the multi-user MIMO system, the base station transmits data to the multi-user. The multi-user MIMO system is different from a single-user based MIMO system in that no cooperation is allowed between users.
In the multi-user MIMO system, a user terminal generally feeds back information about a quantized channel to a base station. When the base station transmits a precoded signal based on fed back channel information, there is a difference between an actual channel vector and a channel vector corresponding to the channel information. Accordingly, an error occurs in a preceding process due to the difference. Specifically, when a signal is transmitted at a high power, a data transmission rate may be reduced due to a noise effect caused by the error.
Channel information, preferably including a larger number of bits, is conventionally fed back to reduce the error. However, when the amount of feedback channel information increases, it also may increase overhead in the communication system. Accordingly, there is a need for a MIMO system and method that can achieve a high data rate with a reasonable amount of feedback channel information.